Molded fuel cell plates with seals

ABSTRACT

A fuel cell unit incorporates a pair of plates; one plate an anode, the other a cathode. Respective anode and cathode plates are physically bonded together to form such pairs; wherein pluralities of the pairs are secured together to form commercially available fuel cells utilized to generate electric power. Seals employed between respective pairs of plates are in the nature of resilient beads arranged about selected areas of the plates to confine paths for fluids adapted to flow within said selected areas. A combination sealing and bonding method for manufacturing such fuel cell units involves the injection of a rapidly curable liquid silicone into aligned mold gating apertures of the respective pairs of the plates, whereby liquid silicone flows through and between the plates to a) seal between respective anode and cathode plates pairs and to b) form an insulation layer on the backside of the anode.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to improved fuel cell assemblies forgenerating electric power, and more particularly to a method forproviding combined sealing media between individual fuel cell plates andinsulation between fuel cell units, all in a single process.

2. Description of the Prior Art

It is known to apply resilient sealing beads to and between the faces offuel cell plates for controlling fluid flows between pluralities of suchplates, stacked in pairs and bolted together for generating electricpower. In a typical fuel cell stack arrangement, the pluralities of suchplates are sandwiched together in a parallel, face-to-face pattern. Theplates are held spaced apart by resilient sealing beads typicallyadhesively bonded to the face of at least one of any two adjoiningplates. The sealing beads fit within grooves on the faces of the plates,and define paths or channels for fluids to flow between the plates.Normally, the fluids include not only fluid electrolytes used forgeneration of energy, but also coolants as will be appreciated by thoseskilled in the art.

The cell plates employed in the usual fuel cell are normally formed ofplastic composites that include graphite. The sealing beads are formedof an elastomeric material. The beads are normally adhesively applied tothe plates by a bonding agent, although in some cases the beads aresimply held in place by pressure of compression created by boltedconnections between plates. Each fuel cell unit is comprised of acathode and an anode plate. Between each cathode and anode plate of eachcell flows a coolant material of either a glycol-based anti-freeze ordeionized water. Between each cell unit flows two chemically reactiveelements, hydrogen and oxygen, separated by a catalytic membrane. Thehydrogen and oxygen elements react at the membrane to form water vaporin a type of reverse electrolysis.

The nature of the chemical reaction, along with a need for separation ofthe coolant from the reacting elements, occasionally requires thatextreme or costly measures be taken to avoid leakage through or betweenthe plates. Thus, an improved mechanism is needed to assure againstleakage between adjacent fuel cell plates, one that is highly reliable,particularly in mass production manufacturing environments.

SUMMARY OF THE INVENTION

A fuel cell apparatus includes a plurality of individual fuel cellunits, each including at least two facing, parallel plates, matedtogether. A resilient sealing media, preferably formed of an elastomericmaterial, is employed to seal the plates together. The sealing media maybe applied in the form of a curable fluid sealing material, which afterbeing cured in place, is adapted to facilitate control of fluid flows,such as coolants between the plates, and of electrolyte flows betweenfuel cells. Upon completion of manufacture, a plurality of suchparallel, stacked plates that incorporate the present invention areseparated by a plurality of discrete resilient sealing beads disposedover selective portions of the surfaces of the two facing plates.

Specifically, the invention involves the manufacture of fuel cell units,each unit defined by a pair of plates comprising an anode and a cathodeplate, in which the cathode plate and the anode plate are sealinglybonded together. Pluralities of such fuel cell units are stacked andsecured together to form commercially available composite fuel cellstructures utilized to generate electric power, either domestically(i.e. for home use) or for use in vehicles.

The invention offers a combination sealing and insulation procedure inwhich pairs of such fuel cell plates may be manufactured in a simple andefficient manner. The method employed involves the injection of arapidly curable liquid silicone into an aligned mold aperture of one ofthe mated plates, whereby liquid silicone may flow via the aperturesthrough the other plate, as well as between the plates in order toestablish a seal between cathode and anode plates. Moreover, the liquidsilicone is injected into aligned mold gating apertures of the cathodeand anode plates, flows entirely through both plates, and forms aninsulation layer on the backside of the bottom plate. In the preferredembodiment described herein, the bottom plate is the anode.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded view of a fuel cell unit of the type described inthe present invention, including anode and cathode plates along withseals adapted for interposition between plates within grooves on theplate faces, and including an insulation layer on the backside of theanode.

FIG. 2 is a fragmentary cross-sectional view of an assembled molded andsealed fuel cell unit of FIG. 1, taken through a corner of an assembledrectangular unit constructed in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1 and 2, a fuel cell unit 10 is shown, which includesand an anode plate 12 and a cathode plate 14. Stacks of such fuel cellunits 10 are assembled together to provide composite fuel cellstructures (not shown) to generate electric power. In such a stack, aninsulation layer 16 is interposed between each fuel cell unit 10.

Elastomeric sealing beads 18, 20 are interposed between each fuel cellunit 10, as well as between each plate 12, 14. Although the beads 18, 20are shown separately in the exploded depiction of FIG. 1, this inventionprovides a means by which the beads will be integrally connected in onesingle, contiguous mass of material as will be explained herein. Inpreferred form, the layer 16 is thicker than the beads 18, 20.

Each of the sealing beads 18, 20 is accommodated by respective grooves22 in the cathode plate 14, and grooves 23 in the anode plate 12. Thesealing beads 18, 20 are contiguous so as to define interior perimeters32 and 34, respectively, adapted to accommodate either a coolant or afuel component. Thus, fuel apertures 24 accommodate the admission andflow of liquid hydrogen into the plate reaction area 38 of the anode 12.Referring specifically to FIG. 2, the anode includes grooves 46 for thispurpose. Conversely, the cathode 14 includes a series of grooves 44which provide a reaction media for oxygen, which is admitted into thearea 38 via fuel apertures 25.

Within the respective plates 12 and 14, the fuel apertures are shown as25A and 25B, and 24A and 24B, respectively, as shown. In the structuresof the unitary sealing beads 18 and 20, fuel apertures for hydrogen areshown as fully circumferential apertures 26A and 26B, while fuelapertures for oxygen are depicted as fully circumferential apertures 28Aand 28B. It will be noted that the respective oxygen and hydrogenapertures accommodate a cross flow over the plate reaction area 38, tothe extent that the apertures are diametrically opposed from each otherwithin the rectangular plates 14 and 12.

It will be appreciated by those skilled in the art that chemicalreactions in the nature of a reverse electrolysis takes place within afuel cell. The reactions are created by the contact between the fuelcomponents of oxygen and hydrogen, and enhanced by a catalytic membrane(not shown) positioned between adjacent stacked fuel cell units 10.Thus, such reactions take place only between the fuel cell units 10.Referring now particularly to FIG. 2, spaced areas between each of themating, parallel faces 13 and 15 of each of the pairs of anodes 12 andcathodes 14, respectively, are defined by inter-plate coolant grooves42. Primary fuel cell cooling thus takes place between each of the matedplates 12 and 14 of each fuel cell unit 10.

Referring now particularly to FIG. 1, coolant ports 36 admit deionizedwater into the coolant grooves 42 between the plates 12 and 14. Theports 36 are shown respectively as 36A and 36B in the plates 14 and 12,and as 36C in the mated insulation layer 16. In the preferred embodimentdetailed herein, the coolant ports are arranged to be medially locatedwithin the plates and across from each other for optimal benefit, asthose skilled in the art will fully appreciate. For this purpose, itwill be noted that the sealing beads 18 and 20 contain portions 30A and30B designed as semi-circles to promote flows of coolant within theircontiguous interior perimeter boundaries 32 and 34, respectively.

A method of manufacturing the fuel cell unit 10 of the present inventioncan be described as follows. Referring specifically to FIG. 2, it willbe noted that the respective sealing beads 18 and 20, as well as theinsulation layer 16, are all formed as a unitary, contiguous mass ofmaterial 40. This approach avoids the need to form separate insulationand sealing bead parts of FIG. 1, and thus reduces costs of manufacture.As earlier noted, the beads and insulation layer are preferably formedof an elastomeric material. For this purpose, a liquid silicone materialmay be injected under pressure through aligned gating apertures 48 and50, which pass respectively through the anode 12 and the cathode 14, asshown in FIG. 2.

A preferred range of manufacturing pressure is 300 to 700 pounds persquare inch at a temperature in the range of 300 to 400 degreesFahrenheit. The respective anode and cathode plates are placed on thefloor of a mold (not shown) with the anode positioned face down, butspaced from, said floor. Liquid silicone is then forced through thegating apertures, 48 and 50, initially through the cathode, at the notedpressures which are sufficient to force the sealing media through andbetween the plates, and including the space between the bottom plate(anode) and the bottom or floor of the mold. The liquid siliconematerial, at the relatively high temperatures noted, will cure within aspan of approximately two minutes.

It is to be understood that the above description is intended to beillustrative and not limiting. Many embodiments will be apparent tothose of skill in the art upon reading the above description. Therefore,the scope of the invention should be determined, not with reference tothe above description, but instead with reference to the appendedclaims, along with the full scope of equivalents to which such claimsare entitled.

What is claimed is:
 1. An electrolytic fuel cell unit comprising twoplates aligned in spaced, parallel facing proximity with one another,each of said plates including at least one aperture adapted for matingalignment with the other, wherein each said aperture of one plate is inalignment with said at least said one aperture of the other plate; afirst resilient sealing media disposed over portions of each of thesurfaces of said plates, said media extending through and from saidapertures, said media adapted to comprise areas of separation of coolantfluid flows between said plates, and wherein each of said areas ofseparation comprises a sealed channel between said plates; a secondresilient media disposed about a non-facing side of one of said plates,said second resilient media having a thickness greater than thethickness of said first sealing media, wherein all of said mediacollectively comprises a unitary, contiguous mass of material passingthrough said apertures and extending between said plates.
 2. Theelectrolytic fuel cell unit of claim 1 wherein one of said platescomprises a cathode, and the other comprises an anode.
 3. Theelectrolytic fuel cell unit of claim 2 wherein both of said resilientsealing media is formed of a liquid silicone material.
 4. Theelectrolytic fuel cell unit of claim 3 wherein said apertures comprisegating apertures for accommodating flow of liquid sealing media into andbetween said plates during the manufacture of said unit.
 5. Theelectrolytic fuel cell unit of claim 4 wherein said liquid siliconematerial is forced under pressure into said gating apertures to formboth said first and second sealing media, and wherein said secondsealing media comprises an insulation layer.
 6. A method of making anelectrolytic fuel cell unit comprising the steps of: a) providing a pairof fuel cell plates aligned in spaced, parallel facing proximity withone another, each having gating apertures adapted for mating alignmentwith the other; b) placing said plates together in said alignment ontothe floor of a mold with a space between bottom plate and said floor; c)forcing liquid sealing media into said gating apertures under pressure,wherein said media flows through and between said plates, and includingsaid space between the bottom plate and the floor of the mold; d)permitting said media to cure; and e) removing said fuel cell plateswith said cured media from the mold.
 7. The method of claim 6 whereinone of said plates comprises a cathode, and the other comprises ananode.
 8. The method of claim 7 wherein said sealing media comprisessilicone material which becomes resilient upon said cure.
 9. The methodof claim 8 wherein said mold pressure is in a range of 300-700 poundsper square inch at a temperature range of 300 to 400 degrees Fahrenheit.10. The method of claim 9 wherein each of said plates further comprise asecond set of aligned apertures spaced from said gating apertures, saidsecond set of apertures adapted for conveyance of electrolytic fluidsand a coolant.